The invention relates to devices for deploying and securing the ends of bypass grafts and for providing a fluid flow passage between at least two vessel regions or other tubular structure regions. More particularly, the invention relates to bypass grafts that are thermally secured at target vessel locations thereby producing a fluid flow passage from the first vessel location through the bypass graft to the second vessel location. The bypass grafts and deployment systems of the invention do not require stopping or re-routing blood flow to perform an anastomoses between a bypass graft and a host vessel. Accordingly, this invention describes sutureless anastomosis systems that do not require cardiopulmonary bypass support when treating coronary artery disease.
Stenosed blood vessels may cause ischemia and lead to tissue infarction. Conventional techniques to treat partially or completely occluded vessels include balloon angioplasty, stent deployment, atherectomy, and bypass grafting. Coronary artery bypass grafting (CABG) procedures to treat coronary artery disease have traditionally been performed through a thoracotomy with the patient placed on cardiopulmonary bypass support and using cardioplegia to induce cardiac arrest. Cardiac protection is required when performing bypass grafting procedures having prolonged ischemia times. Current bypass grafting procedures involve interrupting blood flow to suture or staple the bypass graft to the host vessel wall and create the anastomoses. When suturing or clipping the bypass graft to the host vessel wall, a generally large incision is made through the vessel and the bypass graft is sewn to the host vessel wall such that the endothelial layers of the bypass graft and vessel face each other. Bypass graft intima to host vessel intima apposition reduces the incidence of thrombosis associated with biological reactions that result from blood contacting the epithelial layer of a harvested bypass graft. This is especially relevant when using harvested vessels that have a small inner diameter (e.g.  less than 2 mm).
Less invasive attempts for positioning bypass grafts at target vessel locations have used small ports to access the anatomy. These approaches use endoscopic visualization and modified surgical instruments (e.g. clamps, scissors, scalpels, etc.) to position and suture the ends of the bypass graft at the host vessel locations. Attempts to eliminate the need for cardiopulmonary bypass support while performing CABG procedures have benefited from devices that stabilize the motion of the heart, retractors that temporarily occlude blood flow through the host vessel, and shunts that re-route the blood flow around the anastomosis site. Stabilizers and retractors still require significant time and complexity to expose the host vessel and suture the bypass graft to the host vessel wall. Shunts not only add to the complexity and length of the procedure, but they require a secondary procedure to close the insertion sites proximal and distal to the anastomosis site.
Attempts to automate formation of sutureless anastomoses have culminated in mechanical stapling devices. Mechanical stapling devices have been proposed for creating end-end anastomoses between the open ends of transected vessels. Berggren, et al propose an automatic stapling device for use in microsurgery (U.S. Pat. Nos. 4,607,637; 4,624,257; 4,917,090; and 4,917,091). This stapling device has mating sections containing pins that are locked together after the vessel ends are fed through lumens in the sections and everted over the pins. This stapling device maintains intima to intima apposition for the severed vessel ends but has a large profile and requires impaling the everted vessel wall with the pins. Sakura describes a mechanical end-end stapling device designed to reattach severed vessels (U.S. Pat. No. 4,214,587). This device has a wire wound into a zig-zag pattern to permit radial motion and contains pins bonded to the wire that are used to penetrate tissue. One vessel end is everted over and secured to the pins of the end-end stapling device, and the other vessel end is advanced over the end-end stapling device and attached with the pins. Sauer, et al proposes another mechanical end-end device that inserts mating pieces into each open end of a severed vessel (U.S. Pat. No. 5,503,635). Once positioned, the mating pieces snap together thereby bonding the vessel ends. These end-end devices are amenable to reattaching severed vessels but are not suitable to producing end-end anastomoses between a bypass graft and an intact vessel, especially when exposure to the vessel is limited.
Mechanical stapling devices have also been proposed for end-side anastomoses. These devices are designed to insert bypass grafts, attached to the mechanical devices, into the host vessel through a large incision and secure the bypass graft to the host vessel. Kaster describes vascular stapling apparatus for producing end-side anastomoses (U.S. Pat. Nos. 4,366,819; 4,368,736; and 5,234,447). Kaster""s end-side apparatus is inserted through a large incision in the host vessel wall. The apparatus has an inner flange that is placed against the interior of the vessel wall, and a locking ring that is affixed to the fitting and contains spikes that penetrate into the vessel thereby securing the apparatus to the vessel wall. The bypass graft is itself secured to the apparatus in the everted or non-everted position through the use of spikes incorporated in the apparatus design.
U.S. Surgical has developed automatic clip appliers that replace suture stitches with clips (U.S. Pat. Nos. 5,868,761; 5,868,759; and 5,779,718). These clipping devices have been demonstrated to reduce the time required when producing the anastomosis but still involve making a large incision through the host vessel wall. As a result, blood flow through the host vessel must be interrupted while creating the anastomoses.
Gifford, et al provides end-side stapling, devices (U.S. Pat. No. 5,695,504) that secure harvested vessels to host vessel walls maintaining intima to intima apposition. This stapling device is also inserted through a large incision in the host vessel wall and uses staples incorporated in the device to penetrate into tissue and secure the bypass graft to the host vessel.
Walsh, et al propose a similar end-side stapling device (U.S. Pat. Nos. 4,657,019; 4,787,386; 4,917,087). This end-side device has a ring with tissue piercing pins. The bypass graft is everted over the ring; then, the pins penetrate the bypass graft thereby securing the bypass graft to the ring. The ring is inserted through a large incision created in the host vessel wall and the tissue piercing, pins are used to puncture the host vessel wall. A clip is then used to prevent dislodgment of the ring relative to the host vessel.
The end-side stapling devices previously described require insertion through a large incision, which dictates that blood flow through the host vessel must be interrupted during the process. Even though these and other clipping and stapling end-side anastomotic devices have been designed to decrease the time required to create the anastomosis, interruption of blood flow through the host vessel increases the morbidity and mortality of bypass grafting procedures, especially during beating heart CABG procedures. A recent experimental study of the U.S. Surgical One-Shot anastomotic clip applier observed abrupt ventricular fibrillation during four of fourteen internal thoracic artery to left anterior descending artery anastomoses in part due to coronary occlusion times exceeding 90 seconds (Heijmen, et al. A novel one-shot anastomotic stapler prototype for coronary bypass grafting on the beating heart: feasibility in the pig. J Thorac Cardiovasc Surg. 117:117xe2x80x9425; 1999).
All documents cited herein, including the foregoing, are incorporated herein by reference in their entireties for all purposes.
The present inventions provide sutureless anastomosis systems that enable a physician to quickly and accurately secure a bypass graft to a host vessel or other tubular body structure. In addition, the invention enables the physician to ensure bypass graft stability, and prevent leaking at the vessel attachment points. The delivery systems of the invention do not require stopping or re-routing blood flow while producing the anastomosis as compared to some current techniques that require interrupting blood flow to suture, clip, or staple a bypass graft to the vessel wall.
A need for bypass grafts and delivery systems that are capable of quickly producing an anastomosis between a bypass graft and a host vessel wall without having to stop or re-route blood flow. These anastomoses must withstand the pressure exerted by the pumping heart and ensure that blood does not leak from the anastomoses into the thoracic cavity, abdominal cavity, or other region exterior to the vessel wall.
Current techniques for producing anastomoses during coronary artery bypass grafting procedures involve placing the patient on cardiopulmonary bypass support, arresting the heart, and interrupting blood flow to suture or staple a bypass graft to the coronary artery and aorta. Cardiopulmonary bypass support is associated with substantial morbidity and mortality. The embodiments of the invention are used to position and secure bypass grafts at host vessel locations without stopping or rerouting blood flow. Accordingly, the embodiments of the invention do not require cardiopulmonary bypass support and arresting the heart while producing anastomoses to the coronary arteries. In addition, the invention generally mitigates risks associated with suturing or clipping the bypass graft to the host vessel, namely bleeding at the attachment site and collapse of the vessel around the incision point.
The invention addresses vascular bypass graft treatment regimens requiring end-to-end anastomoses and end-to-side anastomoses to attach bypass grafts to host vessels. The scope of the invention includes systems to position and thermally secure bypass grafts used to treat vascular diseases such as atherosclerosis, arteriosclerosis, fistulas, aneurysms, occlusions, and thromboses. In addition, the systems may be used to bypass stented vessel regions that have restenosed or thrombosed. The bypass grafts and delivery systems of the invention are also used to attach the ends of ligated vessels, replace vessels harvested for bypass grafting procedures (e.g. radial artery), and re-establish blood flow to branching vessels which would otherwise be occluded during surgical grafting procedures (e.g. the renal arteries during abdominal aortic aneurysm treatment). In addition, the invention addresses other applications including arterial to venous shunts for hemodialysis patients, bypassing lesions and scar tissue located in the fallopian tubes causing infertility, attaching the ureter to the kidneys during transplants, and bypassing gastrointestinal defects (e.g. occlusions, ulcers).
One aspect of the invention provides fittings constructed from a metal (e.g. titanium), alloy (e.g. stainless steel or nickel titanium), thermoplastic, thermoset, composite of the aforementioned materials, or other suitable material, and designed to exert radial force at the vessel attachment points to maintain bypass graft patency. The fittings are advanced through the delivery system and are attached to the vessel wall at target locations. The delivery system is a combination of tear-away sheath, dilator, guidewire, and needle designed to be inserted into the vessel at the desired locations. The tubing, hub and valve of the tear-away sheath are configured to split so the entire sheath may be separated and removed from around the bypass graft after attaching the bypass graft to the host vessel. A plunger is used to insert the bypass graft and fitting combination through the sheath and into the vessel. The dilator and needle may incorporate advanced features, such as steering, sensing, and imaging, used to facilitate placing and locating the bypass graft and fitting combination.
In accordance with the invention, the fittings incorporate mechanisms to thermally secure a bypass graft to a host vessel. One fitting configuration produces an anastomosis between a harvested bypass graft and a host vessel such that only the endothelial layer of the bypass graft is exposed to the interior of the host vessel. The invention also describes fittings designed to permit retrograde flow past the anastomosis site so as to maintain flow through the lesion and to branching vessels located proximal to the anastomosis site. A further aspect of the invention provides fittings having branches to accommodate multiple bypass grafts using a single proximal anastomosis.
Fittings and accompanying components constructed from a conductive material may be used as electrodes to deliver radiofrequency energy to tissue contacting the electrode. Radiofrequency energy is applied to each fitting component (unipolar to an indifferent electrode, or bipolar between fitting components) to thermally secure the bypass graft to the vessel wall. Radiofrequency energy produces ohmic heating of adjacent tissue causing it to coagulate to the electrodes and locally shrinking the vessel wall around the fitting to produce an interference fit between the vessel wall and the bypass graft fitting. This not only thermally secures the bypass graft to the vessel wall but also prevents leaking around the bypass graft to host vessel interface.
Still other objects and advantages of the present invention and methods of construction of the same will become readily apparent to those skilled in the art from the following detailed description, wherein only the preferred embodiments are shown and described, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments and methods of construction, and its several details are capable of modification in various obvious respects, all without departing from the invention. Accordingly, the drawing and description are to be regarded as illustrative in nature, and not as restrictive.